GB2454351A

GB2454351A - Vehicle launch transmission system

Info

Publication number: GB2454351A
Application number: GB0819841A
Authority: GB
Inventors: Reid Alan Baldwin
Original assignee: Ford Global Technologies LLC
Current assignee: Ford Global Technologies LLC
Priority date: 2007-11-02
Filing date: 2008-10-29
Publication date: 2009-05-06
Anticipated expiration: 2028-10-29
Also published as: US20090118088A1; CN101424339A; DE102008047912A1; GB0819841D0; US7779714B2; CN101424339B; GB2454351B

Abstract

A method of launching a vehicle having a transmission system which comprises an engine shaft 12, first and second input clutches 14, 18, first and second input shafts 16, 20, a coupler 44, a power path, and an output 22. The method comprises engaging the coupler 44 to connect the first input shaft 16 and the output 22 through the power path, engaging the second input clutch 18 to connect the engine shaft 12 to the second input shaft 20, using a speed provided by a second speed sensor 28 of the second input shaft 20 to determine a desired clutch torque of the first input clutch 14, and actuating the first input clutch 14 to produce the desired torque to complete a drive connection between the engine shaft 12 and the output 22 via the first input shaft 16 and launch the vehicle. The vehicle may be launched in an odd-numbered gear (e.g. first gear) through the first input shaft 16, the second input shaft 20 providing even-numbered and reverse gears.

Description

A SYSTEM AND METHOD FOR LAUNCHING A VEHICLE

This invention relates generally to vehicles having dual clutch powershift transmissions and in particular to a method for launching a vehicle having such a transmission.

A powershift transmission is a geared mechanism that includes no torque converter, but instead employs two input clutches driveably connected to an engine crankshaft. A io powershift transmission produces multiple gear ratios in forward and reverse drive arid transmits power continuously us ng synchronized clutch-to-clutch shi fts.

The transmission incorporates genring arranged in a dual layshaft configuration between the transmission input and its output. One input clutch transmits torque between the input and a first layshaft associated with even-numbered gears, the other input clutch transmits torque between the transmission input and a second layshaft associated with odd-numbered gears. The transmission produces gear ratio changes by alternately engaging a first input clutch and running in a current gear, disengaging the second input clutch, preparing a power path in the transmission for operation in the target gear, disengaging the first clutch, engaging the second clutch and preparing another power path in the transmission for operation in the next gear.

A need exists for continuing to operate a dual clutch powershift transmission when communication between a transmission controller and an engine controller is lost.

This is because shifting the transmission to neutral gear operation is considered a very high severity failure.

it is an object of the invention to provide a method and system for launching a vehicle that satisfies the above need.

According to a first aspect of the invention there is provided a system for launching a vehicle comprising an engine shaft, a transmission including first and second input shafts, first and second input clutches alternately connecting and disconnecting the engine shaft and the first and second input shafts, respectively, an output, a power path including a coupler for driveably connecting the first input shaft and the output through an odd-numbered gear, a speed sensor for producing a signal representing a speed of the second input shaft arid a controller communicating with the speed sensor and configured to engage the coupler and connect the first input shaft and the output mutually through the power path, to engage the second input clutch and connect. the engine shaft and the second input shaft is mutually, to use a speed of the second input shaft to determine a desired clutch torque capacity of the first input clutch and to actuate the first input clutch and produce the desired clutch torque capacity of the first input clutch.

The controller may be further configured to disengage the input clutches before engaging the coupler.

The transmission may further include a second power path including a coupler for driveably connecting the second input shaft and the output through one of an even-numbered gear and reverse and the vehicle may further include a second speed sensor for producing a signal representing a speed of the output and the controller communicates with the second speed sensor and is further confiqured to use the speed of the output to select the second power path.

Selecting the second power path may include controlling the torque transmitted through the second power path.

According to a second aspect of the invention there is provided a method for launching a vehicle having an engine shaft, first and second input clutches, first and second input shafts, a coupler, a power path and an output wherein the method comprises engaging the coupler to connect the first input shaft and the output through the power path, engaging the second input clutch to connect the engine shaft and the second input shaft, using a speed of the second input shaft to determine a desired clutch torque capacity of the first input clutch and actuating the first input clutch to produce the desired clutch torque capacity of the first input clutch and to complete a drive connection between the first input shaft and the output.

The power path may comprise a first power path for connecting the first input shaft and the output through an odd-numbered gear and a first output shaft and the method may comprise engaging the coupler to connect the first input shaft and the first output shaft through the first power path, engaging the second input clutch to connect the engine shaft and the second input shaft mutually, using a speed of the second input shaft to determine a desired clutch torque capacity of the first input clutch and actuating the first input clutch to produce the desired clutch torque capacity of the first input clutch and to complete a drive connection between the first input shaft and the first output shaft through the first power path.

Engaging the coupler to connect the first input shaft and the first output shaft through the first power path may further comprise engaqinq the coupler to connect the first input shaft and the first output shaft through a forward gear of the transmission.

The method may further comprise disengaging the first and second input clutches before engaging the coupler.

The transmission may include a second power path.

The method may further comprise using a speed of the output to select Lhe second power path.

Selecting the second power path may include controlling Lhe torque transmitted through the second power path.

The second power path may include a second output shaft and the method may further comprise engaging a coupler to connect the second input shaft and the second output shaft through a reverse gear of the transmission.

The second power path may connect the second input shaft and the output through an even-numbered gear and the method may further comprise iisng a speed of the output to select the second power path.

The invention will now be described by way of example with reference to the accompanying drawing of which:-Figure 1 is a schematic diagram showing a dual clutch powershift automatic transmission; Figure 2 is state diagram illustrating the subject control strategy; and Figure 3 is a schematic diagram of a system for controlling a vehicle launch using a dual clutch transmission, such as that shown in Figure 1.

Referring now to Figure 1, a dual clutch power shift transmission 10 is draveably connected to the crankshaft 12 of an engine or a shaft driven by another power source such as an electric motor.

A first input friction clutch 14 alternately connects and disconnects shaft 12 and a first input shaft 16 as clutch 14 is engaged arid disengaged, respectively.

A second input friction clutch 18 alternately connects and disconnects shaft 12 and a second input shaft 20 as clutch 18 is engaged and disengaged, respectively.

A first set of selectable power paths which produce odd-numbered gears of the transmission, connect first input shaft 16 to a load, such as the driven wheels (not shown) of a motor vehicle through a powertrain that may include a drive shaft, differential mechanism and axle shafts. The first. or third gear power paths are activated by moving coup!er 44 to connect gear 34 or 38, respectively, to lower output shaft 22. Similarly, a fifth gear power path s activated by moving coupler 52 to connect gear 42 to upper output shaft 24.

A second set of selectable power paths, which produce even-numbered gears of the transmission connect second input shaft 20 to the load. The second or fourth gear power paths are activated by moving coupler 46 to connect gear 48 or 50 respectively to output shaft 22. The reverse gear power path is activated by moving coupler 52 to connect gear 54 to upper output shaft 24. When couplers 46 and 52 are in the neutral position, no drive connection between input shaft 20 and the load exists.

A first speed sensor 26 produces an electronic signal representing the rotational speed of input shaft 16. The second speed sensor 28 produces an electronic signal representing the rotational speed of input shaft 20. A third speed sensor 30 produces an electronic signal representing the rotational speed of output shaft 24.

The first gear power path includes a pinion 32 secured to input shaft 16, a first gear output 34 journalled on output shaft 22 and in continuous meshing engagement with pinion 32 and the coupler 44.

The third gear power path includes a pinion 36 secured to input shaft 16, a third gear output 38 -journalled on output shaft 22 and in continuous meshing engagement with pinion 36 and the coupler 44.

The fifth gear power path includes a pinion 40 secured to input shaft 16, a fifth gear output 42 journalled on output shaft 24 and in continuous meshing engagement pinion 40 and the coupler 52.

The second gear power path inc'udes a pinion 94 secured to input 20, a gear 96 in continuous meshing engagement with pinion 94 and icfler 98 which is secured to gear 96 mutually and journalled on output shaft 22 and the coupler 46.

A fourth gear power path includes pinion 48, secured to input shaft 20, a fourth gear output pinion 50 journalled on output shaft 22 and in continuous meshing engagement pinion 48 and the coupler 46.

The reverse gear power path includes the pinion 94, gear 96, idler 98 and reverse output gear 54 which is journalled on output shaft 24 and is in continuous meshing engagement with idler 48 arid the coupler 52.

Coupler 44 includes a selector sleeve, which moves leftward to engage clutch teeth on the first gear output 34, and moves riqhtward to enqaqe clutch teeth on the third gear output 38. Coupler 44 produces a drive connection between gears 34 and 38 and output shaft 22, depending upon the direction that the selector sleeve is moved.

Similarly, coupler 46 includes a selector sleeve that moves leftward to produce a drive connection between fourth gear output 50 and output shaft 22 and moves rightward to produce a drive connection between idler 48 and output shaft 22. The idler 48 is secured to a sleeve shaft 99 by which output gear 96 is journalled on output shaft 22.

Coupler 52 includes a selector sleeve that moves leftward to produce a drive connection between fifth gear output 42 output shaft 24 and moves rightward to produce a drive connection between reverse gear output 54 and output shaft 24.

The gears 56, 58 are both in continuous meshing engagement with a common output ring gear (not shown), thereby mutually connecting upper output shaft 24 and lower output shaft 22 such that the transmission includes a single output connected to a driven load.

Couplers 44, 46 and 52 are preferably synchronizers of the type used in automotive manual transmissions to connect a gear or pinion to a shaft, after synchronizing the speed of the shaft and that of the pinion or gear. Each coupler may also disconnect the shaft and the associated pinion or gear. Alternatively, each coupler may be a dog clutch having teeth that are engaged with dog teeth on a gear or pinion. This invention may use couplers in any combination of synchronizers and dog clutches. Each coupler is composed of a hub secured to the shaft and a sleeve which is supported on the hub for sliding movement leftward or rightward into engagement with dog teeth on the adjacent gear or pinion. In the case where a coupler is a synchronizer, it is provided with a conical surface, which engages mutually with a corresponding conical surface located on the gear or pinion. When the synchronizer is engaging either of its adjacent gears, the conical surfaces are forced together into frictional contact and that frictional engagement synchronizes the speed of the gear to that of the shaft before the dog teeth engage. Other types of synchronizers or couplers may also be used.

Peferr:inq now to Figure 2, the vehicle can be launched, i.e. accelerated from a stopped or nearly stopped condition, using the first gear power path beginning with an initial transmission state 60, in which input clutches 14, 18 and couplers 44, 46, 52 are disengaged, thereby connecting no power path to the output shafts 22, 24.

Transmission 10 is prepared to launch the vehicle when placed in a second state 62, in which the selector sleeve of coupler 44 is moved leftward to connect first gear output 34 to the output shaft 22, input c]utch 18 s engaged, all couplers associated with the even numbered gears remain disengaged, and input clutch 14 remains disengaged.

In the next state 64, transmission 10 completes the engagement of first gear that launches the vehicle. Coupler 44 remains engaged and connecting first gear output 34 to output shaft 22, input clutch 18 remains engaged driving input shaft 20 at the speed of engine shaft 12, couplers 46 and 52 remain disengaged and the torque capacity of the first input clutch 14 is increased as a function of the speed of the second input shaft 20, as represented by the signal produced by speed sensor 28. The speed of first input shaft 16 is then equal to the speed of second input shaft 20.

Speed sensor 28 is a surrogate for an engine speed sensor. It is assumed that the engine throttle is either mechanically connected to the accelerator pedal or is controlled by an engine controller as a function of accelerator pedal position.

A forward launch of the vehicle is completed in transmission state 66, in which the even-numbered and odd-numbered gears are selected sequentially based on the speed of the output shaft as represented by the signal produced by speed sensor 30. The output shaft speed, which is less than a reference speed for the current gear, is fed forward to select the next gear.

When a gear is selected, its corresponding coupler connects the selected gear to its output shaft, the input clutch associated with the off-going gear is disengaged, and the input clutch associated with the oncoming gear is engaged.

Although the method has been described with reference to a vehicle launch in first gear, the launch can he executed using the reverse gear power path beginning with an initial transmission state, in which input clutches 1.4, 18 and couplers 44, 46, 52 are disengaged, thereby connecting no power path to the output shafts 22, 24.

Transmission 10 is prepared to launch the vehicle in reverse when the selector sleeve of coupler 52 is moved rightward to connect reverse gear output 54 to the output shaft 24, input clutch 14 is engaged, all couplers associated with the odd-numbered gears remain disengaged, and input clutch 18 remains disengaged.

The transmission 10 completes the engagement that launches the vehicle in reverse when coupler 52 remains engaged and connecting reverse gear output 54 to output shaft 22, input clutch 14 remains engaged and driving input shaft 16 at the speed of engine shaft 12, couplers 44 and 46 remain disengaged, and the torque capacity of the second input clutch 18 is increased as a function of the speed of the first input shaft 16, as represented by the signal produced by speed sensor 26.

Figure 3 illustrates schematically an engine 70 controlled by an electronic engine control module 72 (ECM), which issues commands that control operation of the engine.

-10 -The engine controller 72 receives input from various sensors including a sensor 74, which produces an electronic signal representing the degree to which an accelerator pedal 76 is depressed and a sensor 78, which produces a signal representing the speed of engine crankshaft 12.

The engine controller (CCM) 72 communicates by a data bus 80 with an electronic transmission control module 82 (r1CM) which issues commands that control operation of the input clutches 14, 18 and couplers 44, 46, 52 in response to the results produced by executing transmission control algorithms. Data used in the execution of the algorithms is received as input from various e'ectronic signals including speed sensors 26, 28, 30 and engine speed transmitted on bus 80 from ECM 72. Stored in electronic memory accessible to the CPU of TCM 82 is a function 84 in the form of a lookup table indexed by engine speed and the oncoming gear in which the vehicle will be launched, the function containing a desired torque capacity of the input clutch that corresponds to the oncoming gear.

A conventional control strategy would set the torque capacity of the launch clutch as a function of engine speed.

But, in the event communication of the current engine speed to TON 82 is faulty or absent, the control strategy for launching the vehicle uses the surrogate input signals from sensor 28 for a launch in first gear or sensor 26 for a launch in reverse thereby preventing a failure to launch.

Therefore in summary, in order to meet the above

referred to need there is provided a system having a controller operable to execute a method including engaging a coupler to connect a first input shaft and a first output shaft through a power path, engaging a second input clutch to connect an engine shaft and a second input shaft mutually, using a speed of a second input shaft to determine a desired clutch torque capacity of a first input clutch and -11 -actuating the first input clutch to produce the desired clutch torque capacity of the first input clutch and to complete a drive connection between the first input shaft and the output.

Therefore, in the event that communication between a transmission controller and an engine controller is lost or flawed, the control method arid system engage an input clutch to connect the engine shaft and a second input shaft other than the first input shaft, which is associated with the on-coming gear to be engaged during the vehicle launch. In this way, the speed signal of the second input shaft accurately represents engine speed, is transmitted to the transmssi.on controller, and is used to produce a desired torque capacity of the first input clutch.

The strategy requires an engine speed signal only during launch. Output speed is used to schedule gear shifts. All even gears are deselected during vehicle launch and the even-numbered gear clutch is closed. Under those conditions, the even-numbered gear input shaft speed sensor is used as the engine speed sensor.

The control strategy launches a vehicle equipped with a dual clutch transmission when communications between the engine controller and the transmission controller have been interrupted.

Claims

-12 - CLAIMS

1. A system for launching a vehicle comprising an engine shaft, a transmission including first and second input shafts, first and second input clutches alternately connecting and disconnecting the engine shaft and the first and second input shafts, respectively, an output, a power path including a coupler for driveably connecting the first input shaft and the output through an odd-numbered gear, a speed sensor for producing a signal representing a speed of the second input shaft and a controller communicating with the speed sensor and configured to engage the coupler and connect the first input shaft and the output mutually through the power path, to engage thes econd input clutch and connect the engine shaft and the second input shaft mutually, to use a speed of the second input shaft to determine a desired clutch torque capacity of the first input clutch and to actuate the first input clutch and produce the desired clutch torque capacity of the first input clutch.

2. A system as claimed in claim 1 wherein the controller is further configured to disengage the input clutches before engaging the coupler.

3. A system as claimed in claim 1 or in claim 2 wherein the transmission further includes a second power path including a coupler for driveably connecting the second input shaft and the output through one of an even-numbered gear and reverse, the vehicle further includes a second speed sensor for producing a signal representing a speed of the output and the controller communicates with the second speed sensor and is further configured to use the speed of the output to select the second power path.

4. A method for launching a vehicle having an engine shaft, first and second input clutches, first and second -13 -input shafts, a coupler, a power path and an output wherein the method comprises engaging the coupler to connect the first input shaft and the output through the power path, engaging the second input clutch to connect the engine shaft and the second input shaft, using a speed of the second input shaft to determine a desired clutch torque capacity of the first input clutch and actuating the first input clutch to produce the desired clutch torque capacity of the first input clutch and to complete a drive connection between the first input shaft and the output.

5. A method as claimed in claim 4 wherein the power path comprises a first. power path for connecting the first input shaft. and the output through an odd-numbered gear and a first output shaft and the method comprises engaging the coupler to connect the first input shaft and the first output shaft through the first power path, engaging the second input clutch to connect the engine shaft and the second input shaft mutually, using a speed of the second input shaft to determine a desired clutch torque capacity of the first input clutch and actuating the first input clutch to produce the desired clutch torque capacity of the first input clutch and to complete a drive connection between the first input shaft and the first output shaft through the first power path.

6. A method as claimed in claim 5 wherein engaging the coupler to connect the first input shaft and the first output shaft through the first power path further comprises engaging the coupler to connect the first input shaft and the first output shaft through a forward gear of the transmission.

7. A method as claimed in any of claims 4 to 6 wherein the method further comprises disengaging the first and second input clutches before engaging the coupler.

-14 -

8. A method as claimed in any of claims 4 to 7 wherein the transmission includes a second power path.

9. A method as claimed in claim 8 wherein the second power path includes a second output shaft and the method further comprises engaging a coupler to connect the second input shaft and the second output shaft through a reverse gear of the transmission.

10. A method as claimed in claim 9 wherein the second power path connects the second input shaft and the output through an even-numbered gear and the method further comprising the step of using a speed of the output to select the second power path.

11. A system for launching a vehicle substantially as described herein with reference to the accompanying drawing.

12. A method for launching a vehicle substantially as described herein with reference to the accompanying drawing.